Title: A method to utilize the Low grade manganese ore fines into
ferromanganese production.
FIELD OF THE INVENTION:
This invention relates to a method for utilizing low grade manganese ore
fines for producing ferromanganese comprising: subjecting low grade
ferromanganese ore fines to the step of beneficiation to remove alumino
silicates & iron;
classifying the ores into fines and coarse crushing the coarse content and
passing the same high intensity magnetic separator,
subjecting the concentrate to the step of briquetting;
shaping the briquettes.
BACKGROUND OF THE INVENTION:
The silicates present in the ores play important role in adjusting the slag
chemistry for better slag metal separation in the ferromanganese making
process. Slag properties depend on ratio of MnO: SiO2 and alumina content.
Maintaining the MnO:SiO2 is more important for better slag properties and
in conventional methods it is balanced by adding the silious ores in the feed.
The low grade fines contain high slica and can be best option for the
maintaining the slag chemistry.

The magnetic separation process removes the nonmagnetic gangues at high
intensity magnetic separation in the first stage and the recovered product can
be upgraded to improve Mn/Fe ration by medium intensity magnetic
separation. The recovered ore concentrate can be briquetted using the
optimum combination of molasses, cement and bentonite binder.
Manganese ores are primarily used in the ferromanganese making. These
ferroalloys are used in steel making process to refine the steel. Quality of
ferromanganese depends on the feed grade ores and the ore should contain
Mn: 38-48% and Mn/Fe ~5 to produce the high carbon ferromanganese. The
mined high-grade manganese ore lumps (+10mm) are used in the submerged
arc furnace at ferromanganese plant. The low-grade fines generated in the
mining and sizing of the high grade manganese ores, are disposed at waste
dumps. These fines usually contain Mn: 25-37% and Mn/Fe: 1-3. The high-
grade manganese ore resources are depleting rapidly and there is an
economic sense to beneficiate the low-grade manganese ore fines to generate
the ferromanganese grade ores. Beneficiation process require the size
reduction whereas, a suitable agglomeration method is required to utilize
these fines into submerged arc furnace operation. Low-grade manganese ore
fine samples were collected from Keonjhar district of Orissa and a process
flowsheet has been developed to recover the siliceous ferromanganese grade
ore concentrate. The recovered ore concentrate was briquetted and used into
ferromanganese making process to replace the high grade lumpy ores as well
as to maintain the better slag properties.

Problems with the Prior Art
1. The conventional fine beneficiation methods are based on the specific
gravity deference but these methods do not work when iron is present
as a gangue mineral because of the narrow specific gravity difference
between Mn and Fe.
2. The wet magnetic separation generates large amount of tailings as a
waste, which is an environmental concern and reduction roasting
followed by low intensity magnetic separation is a costly process.
3. The conventional agglomeration process are costly as required very
finer size material (pelletization) or use high temperature (>1000°C)
for bonding.
4. Conventional binders are not efficient for the manganese ores
briquetting because manganese ore pass through various phases
(Mn02, Mn304 and MnO) during the smelting reduction process in
the furnace which require high strength agglomerate.
5. The silica adjustment for slag separation is done using the siliceous
ores which become costly and increases the overall processing cost.
OBJECTS OF THE INVENTION:
An object of this invention is to propose a method to utilize the low grade
ferruginous manganese ore fines for producing ferromanganese;

Another object of this invention is to propose a briquetting process for
agglomeration of manganese ore fines;
Further, object of this invention is to propose a cheap or process which
decreases the over all processing cost.
SUMMARY OF THE INVENTION:
According to this invention there is provided a method to use low grade
ferruginous manganese ore fines for producing ferromanganese comprising:
subjecting low grade ferromanganese ore fines to the step of beneficiation to
remove alumino silicates & iron;
classifying the ores into fines and coarse crushing the coarse content and
passing the same high magnetic separator,
subjecting the concentrate to the step of briquetting;
shaping the briquettes.
DETAILED DESCRIPTION OF THE INVENTION:
Substantial amount of ferromanganese grade ore concentrate can be
recovered from low grade manganese ore fines generated in the mining.
Physical beneficiation methods have been used here to beneficiate these ore
fines. Low grade manganese ore fines of 0-10mm with Mn 25-37%, Mn/Fe:
<3 Si02: 6-37%, A1203: 2-7 was beneficiated to remove aluminosilicates
and iron content. The ores were wet classified at 0.5mm to remove

aluminosilciates in the fines and the coarse content was crushed to <3mm
and further the material was passed through the high and medium intensity
magnetic separator. In the first stage at > 17000 gauss the nonmagnetic
minerals including auminosilicates removed. The recovered magnetic
fraction contains manganese and iron minerals, which is then, passed though
the high intensity magnetic separator at 11000 gauss to separate the
manganese and iron minerals to improve Mn/Fe ration which is very critical
for grade of ferromanganese produced. A product of Mn >42, Mn/Fe: ~5 and
Si02 > 10, and AI203 <3% is thus achieved by this innovative process with
the manganese recovery >35% and the weight recovery was 25-31%.
The concentrate recovered was briquetted using the molasses (7-10%),
Portland cement (4-7%) and bentonite (1-2%). The pillow shape briquettes
produced using the roll briquetting press (cold compressive strength: 60-
lOOkgf/briq, Drop Index: >90%, Hot CCS: 25-37kgf/briq and Soft. Tempt.:
~1000°C) was used for feed for the ferroalloy plant. These briquettes have
suitable properties for plant application.
The process developed for utilization fines is novel and cheapest. The
impact of the process is more profound as it produces the product as
siliceous ore concentrate for adjustment of slag chemistry to improve
process efficiency. The developed process provides the methodology for
proper utilization of natural resources.

It is necessary to have detailed information of the liberation and association
characteristics of minerals before adjusting the process parameters and also
achieving desire quality product.
The first stage of the process is to crush the oversize fines (>10mm) into 0-
3mm size. Further fine grinding will result in the loss of softer pyrolusite
particles in the magnetic fraction with iron particles. This size range is
suitable for optimum dry separation of manganese, iron and aluminosilicate
gangue minerals. This size is suitable for briquetting and minimize the
grinding cost of the process.
The crushed product was passes through high intensity magnetic separator to
separate the magnetic (iron) and weakly magnetic (locked Mn & Si02 and
manganese silicates) nonmagnetic (aluminosilicates). Manganese and iron
minerals present in the ore are feebly magnetic and silica and
aluminosilcates are non magnetic. At high intensity at > 17000 gauss the
nonmagnetic aluminosilicates and free quartz particles segregated in
nonmagnetic fraction. The iron, manganese and quartz particle coated with
iron minerals report in magnetic fraction. This process rejects 20-25%
weight material and reduces alumina and silica level in the ore concentrate.
The gangues contain silica and alumina is removed in the first stage of
magnetic separation and recovered magnetic fraction is passed though the
magnetic separator at 11000 gauss. The free iron particles, iron manganese
locked and iron coated silica particles reports in the magnetic and

manganese, locked manganese quartz and free quartz report in the non
magnetic fraction. The iron present in the manganese mineral spinal
((Mn++, Fe++, Mg) (Fe+++, Mn+++) 204) and finely disseminated in the
manganese report in the nonmagnetic fraction. The Mn/Fe ratio of the ores
depends on the operational parameter of the magnetic separator also.
A product of Mn > 42, Mn/Fe: ~5 and Si02 > 10 and was achieved in this
process with the manganese recovery >35% and the weight recovery was
30-40%. The quartz particles locked with the manganese particle and Si02
present in the braunite manganese mineral controls the silica content in the
ores. These ores can be used as a sweetener to improved MnO: Si02 ratio in
the ore burden in the furnace used for ferromanganese production. The
adjustment of slag chemistry will improve slag properties and will result in
better operating conditions. The recovered ore concentrates are relatives
cheaper and will provide flexibility to adjust MnO: Si02 ratio than the
merely siliceous manganese ores (MnO.Si02).
Briquetting of Ore fines were prepared using different binders and properties
of the briquettes were measured. Molasses ( 0-10%), cement (0-10%) and
bentonite (0-5%) combinations were optimized to identify a most suitable
combination. Molasses play important role to achieve the green strength for
initial handling during the briquetting process. Whereas, added cement and
bentonite combination improve the overall cold and hot compressive
strength of the briquettes for the improved performance in the smelting
reduction process.

The drop strength of briquettes from one meter height varies between 2 to 6
drops and cold compressive strength was found between 70 to 240kg/cm .
These briquettes were isothermally heated at 700°C for 25 minutes and the
compressive strength of the sample were measured in the hot condition. Hot
compressive strength of the briquettes was found between 50 to 150kg/cm .
The best techno economic binder combination was 7,4 and 1% molasses,
cement and bentonite, respectively.
The pillow shape briquettes produced using the roll briquetting press (cold
compressive strength: 60-100kgffbriq, Drop Index: >90%, Hot CCS: 25-
37kgf/briq and Soft. Tempt.: ~1000°C) was used for feed for the ferroalloy
plant. These briquettes are suitable as a feed for the submerged arc furnace
operation in the ferromanganese making. The process flow sheet is given in
figure 1.

WE CLAIM:
1. A method to utilize the low grade ferruginous manganese ore fines for
producing ferromanganese comprising:
subjecting low grade ferromanganese ore fines to the step of
beneficiation to remove alumino silicates & iron;
classifying the ores into fines and coarse crushing the coarse content
and passing the same high magnetic separator,
subjecting the concentrate to the step of briquetting;
shaping the briquettes.
2. The method as claimed in claim 1, wherein the low grade manganese
ore fines comprises of 0-10mm with Mn 25-37%, Mn/Fe: <3 SiO2: 6-
37%,A1203:2-7.
3. The method as claimed in claim 1, wherein the said step of briquetting
is preferred using the molasses (7-10%), Portland cement (4-7%) and
bentonite (1-2%).
4. The method as claimed in claim 1, wherein the said step of briquetting
is preferred in a roll briquetting press.

A method for producing ferromanganese from low grade ferruginous
manganese ore fines comprising: subjecting low grade ferromanganese ore
fines to the step of beneficiation to remove alumino silicates & iron;
classifying the ores into fines and coarse crushing the coarse content and
passing the same high magnetic separator, subjecting the concentrate to the
step of briquetting; shaping the briquettes.